1. Field of the Invention
The present invention relates to a selective call radio paging receiver having display function used in mobile communication, for example.
2. Description of the Prior Art
A conventional selective call radio paging receiver has a memory erase mode switch separate from an operation start switch and a memory read switch and is so configured that the memory erasing may be performed by using an execution switch which functions as the memory read switch.
FIG. 5 shows configuration of a conventional selective call radio paging receiver of this type. In FIG. 5, numeral 1 denotes an antenna, 2 a radio receiver, a decoder, 4 an individual memory (P-ROM) for exclusive use, 5 a liquid crystal display device (LCD), 6 a driver, 7 a speaker, 8 power supply, 9 a quartz oscillator, 10, 11 and 12 switches.
The switches 10, 11 and 12 are connected to the decoder 3 and function to indicate control conditions. That is to say, the switch 10 performs start of initial operation accompanied by initial display. The switch 11 performs suspension of ringing, suspension of display and start of the liquid crystal display device 5, readout of message information, and erase execution. The switch 12 performs setting memory erase mode.
As shown in FIG. 6, the decoder section 3 comprises an SC collator 31 for comparing a signal 221 received from the radio receiver 2 with a fixed frame synchronizing signal SC (Synchronization Codeword), an ID collator 32 for comparing succeeding contents of the received signal 221 with a selective calling number in its own frame, a message decoder circuit 33 for extracting message data 331 out of further succeeding contents of the received signal 221, a message memory 34 for storing a decoded message, and a controller 35 for controlling them.
The controller 35 supplies the stored message information to an LCD controller 36 and supplies ringing start information and ringing suspension information to ringing tone generator 37. At this time, the switches 10, 11 and 12 input the above described control conditions to the controller 35. The controller 35 exercises control so as to make the message memory 34, the LCD controller 36 and the ringing tone generator 37 perform predetermined operation. Further, a clock generated by a quartz oscillator 9 and an oscillator 38 is supplied to the control section 35 as the clock for taking in data, processing and control operation.
FIG. 7 logically shows the message memory control operation conducted in the decoder 3. The message data signal 331 is temporarily saved into a temporary message data storage 401 and then stored into one of memories 404a to 404n by a memory storage decision circuit 402. Setting of memory flags 405a to 405n is also performed. The memory flags 405a to 405n are used to judge whether message data of the memories 404a to 404n corresponding thereto are valid or invalid. The memories 404a to 404n comprise shift registers, for example. The memory flags 405a to 405n comprise R-S flip-flops.
In response to respective memory enable condition signals 411a to 411n supplied from the memory storage decision circuit 402, AND gates 403a to 403n exercise control to transfer the message data stored in the temporary message data storage 401 to the memories 404a to 404n. In case the message data stored in the temporary message data storage 401 is to be transferred to the memory 404a, for example, the memory enable condition signal 411a is set at "1" and the signals 411b to 411n are set at "0". Thus only the AND gate 403a is enabled, and transfer is performed without destructing contents of other memories 404b to 404n. By repeating such operation, setting can be performed with respect to some of the memories 404a to 404n and the memory flags 405a to 405n.
The procedure for erasing message data will now be described. After operation has been started by the switch 10, an erase enable flag 408 is set by the switch 12, and a timer 409 is started concurrently therewith. The timer 409 is a Johnson counter, for example. The output of the timer 409 obtained after a predetermined time resets the erase enable flag 408. If a push switch pulse circuit 407 activated by the switch 11 outputs a pulse "1" when the erase enable flag 408 is valid, i.e., the output of the erase enable flag is "1", an AND gate 406 outputs reset signals to the memory flags 405a to 405n.
In the above described conventional selective call radio paging receiver apparatus as well, it is thus possible to erase message data stored in the memories 405a to 404n by setting a memory erase mode by means of the switch 12 and executing memory erase by means of the switch 11.
In recent years, integrated circuit techniques and high density packaging techniques have significantly advanced. In the selective call radio paging receiver apparatus of this kind as well, realization of an apparatus diversified in function, reduced in size and lowered in cost is demanded. Especially for mechanical parts such as switches, however, the effort that went into reduction of size and cost approaches its limit. A low-cost apparatus capable of having diversified functions without increasing the number of such switches and capable of providing manipulation easiness maintained favorably is desired.
In regard to such a desire, the above described conventional apparatus has a problem that packaging of parts for size reduction is difficult and cost increase is incurred because three switches 10, 11 and 12 for assignment of multiple functions are used.
Further, it is sufficient that the selective call radio paging receiver undergoes operation start manipulation once a day and stores received messages corresponding to a day. For call signal receiving exceeding the message information storage capacity, information may be successively erased beginning with the oldest message information. In case such message information erasing is performed by means of switch manipulation, it is desired that message information is not simply erased even if a switch is turned off by false manipulation of the switch. Further, it is desired that memory erasing can be performed by means of predetermined manipulation in case all of the message information has been confirmed or all of the message information is desired to be erased on the following day.
In many of conventional apparatuses as described above, however, a switch of integral type having three slide positions and a push button is typically used as the function assigning switch. When switching from N (normal position) among three slide positions to M (Non-Alert receiving position) is performed, therefore, false switching to OFF (receiving stop position) is often caused. Message information stored in the memory is thus often erased unintentionally, resulting in a problem.
The present invention aims at solving the above described problems of the prior art. An object of the present invention is to provide a low-cost selective call radio paging receiver having display function which allows assignment of multiple functions without increasing the number of switches and which does not hamper the ease of manipulation.